Various embodiments relate generally to dye sublimation inks. More specifically, various embodiments relate to printing systems, methods, and dye sublimation ink formulations for transferring images onto complex-shaped objects.
Dye sublimation inks have long been used for printing on polyester-based materials and objects. Conventionally, sublimation printing processes have used thermal printers and dye transfer paper and have employed analog printing methods. The dye sublimation inks include a pigment suspended in a liquid solvent, such as water. Inkjet inks and inkjet printers have also recently been used for sublimation printing processes.
The market for digital textile printing has grown substantially in recent years. This has led to increased usage of and interest in solvent-based, e.g. water-based, dye sublimation inks. Outside of textile applications, other polyester-based materials are also decorated using dye sublimation technology. Examples include films, containers, packaging, and materials having a polyester coating, such as wood or metal.
Two types of printing processes can be used in sublimation printing. Direct printing requires that ink is jetted directly onto a substrate, cured, and then thermally treated such that the dye diffuses from the ink into the substrate. Indirect printing requires that ink is printed onto heat-resistant transfer paper or another transfer material and cured, e.g. via UV radiation. The transfer paper is placed over a substrate and heat is applied that causes the dye to transfer to the substrate from the transfer paper and form an image.
Indirect printing is both more costly and more complex due to the presence of the transfer paper. Moreover, the transferring process can be materially hindered if the image is not printed onto a flat substrate.
Conventionally, both direct and indirect printing have been carried out only on flat substrates. Because print quality of direct printing relies on accuracy of ink drop placement, the distance between the printer head and the substrate is critical. The distance, which is generally a few millimeters or less, must be kept constant or nearly constant to limit the effects of velocity variability, airflow, etc., on drop placement. Similar issues plague indirect printing. It is often difficult, if not impossible, to conform transfer paper to complex shapes.
Introduced herein are systems and methods for sublimation printing on complex-shaped surfaces. Various printing systems described herein print an image onto a flexible transfer material using a flexible ink formulation. A flexible transfer material, such as a rubber former or thermoformable material, can be used to transfer images to a complex-shaped, i.e. non-planar, substrate. Oftentimes, the image is pre-distorted to take into account the final shape of the transfer material after sublimation. The flexible ink may be, for example, a thermoformable or superflexible ultraviolet (UV) dye sublimation ink.
In some embodiments, the printing systems described herein cure the image jetted onto the transfer material before the image is transferred to the substrate. Consequently, the printing systems may include a light source configured to cure some or all of the ink deposited on the transfer material by a printer head. The light source can be configured to emit UV radiation of subtype V, subtype A, subtype B, subtype C, or some combination thereof.
The transfer material, including the image, can then be formed to fit the substrate and pressed onto the surface of the substrate. In some embodiments, a mold or heat-resistant material, e.g. sand, is used to apply pressure to the transfer material. The substrate typically includes polyester or has a polyester-based coating/spray applied prior to printing. Once the transfer material is pressed onto the substrate, heat is applied to the substrate, the transfer material, or both that is sufficient to cause the ink to sublimate. Sublimation causes at least some of the dye within the ink to permeate the substrate and form a finalized image.
In some embodiments, the flexible ink used to create the image includes a soluble or solvent-sensitive component that allows residual ink to be easily removed, e.g. by a washing process, following sublimation. For example, a solvent may be jetted onto the substrate and/or transfer material that substantially removes residual ink that did not permeate the substrate during sublimation.
Various embodiments are described herein that relate to printing on complex-shaped objects. More specifically, various embodiments relate to printing systems and methods for transferring images to complex-shaped substrates using flexible dye sublimation ink technology and flexible former materials.
The printer head 106 is configured to deposit ink onto a transfer material 104 in the form of an image 110. The transfer material 104, which may also be referred to as a former material, is flexible, which allows the image 110 to be transferred to complex-shaped substrates. For example, the transfer material 104 may be a rubber former, a thermoformable material, etc. In some embodiments, the printer head 106 is an inkjet printer head that jets ink onto the transfer material 104 using, for example, piezoelectric nozzles. Thermal print heads are generally avoided in an effort to avoid premature sublimation of the ink. In some embodiments, the ink is a solid energy, e.g. UV, curable ink. However, other inks may also be used, such as water-based energy curable inks or solvent-based energy curable inks. The ink can be deposited in different forms, such as ink droplets and colored polyester ribbons.
In some embodiments, one or more light sources 112 cure some or all of the ink deposited on the transfer material 104 by emitting UV radiation. The light source(s) 112 may be, for example, a UV fluorescent bulb, a UV light emitting diode (LED), a low pressure, e.g. mercury (Hg), bulb, or an excited dimer (excimer) lamp and/or laser. Various combinations of these light sources could be used. For example, a printing system 100 may include a low-pressure Hg lamp and a UV LED. As will be discussed below with respect to
The printer head 106 and light source 112 are illustrated as being directly adjacent to one another, i.e. neighboring without any intervening components. However, additional components that assist in printing, curing, etc., may also be present. For example, multiple distinct light sources 112 may be positioned behind the printer head 106.
In some embodiments, one or more of the aforementioned components are housed within one or more carriages. For example, the printer head 106 can be housed within a printing carriage 108, the light source 112 can be housed within a curing carriage 114, etc. In addition to protecting the components from damage, the carriages may also serve other benefits. For example, curing carriage 114 can limit what portion(s) of the transfer material 104 and image 110 are exposed during the curing process. The printing system 100 may comprise pulleys, motors, rails, and/or any combination of mechanical or electrical technologies that enable the carriages to travel along the transfer belt 102, i.e. with respect to the transfer material 104. In alternative embodiments, the carriages can be fixedly attached to a rail or base of the printing system 100. In these embodiments, the transfer material 104 can be moved in relation to the printer head 106, light source 112, etc., such that ink can be deposited on the transfer material 104.
In various embodiments, some or all of the components are controlled by a computer system 116, e.g. computer system 700 of
The printer head 202 can include distinct ink/color drums, e.g. CMYK, or colored polyester ribbons that are deposited on the surface of a transfer material 206. Path A represents the media feed direction, e.g. the direction in which the transfer material 206 travels during the printing process. Path D represents the distance between the printer head 202 and the surface of the transfer material 206.
As described above, both direct and indirect printing have conventionally been carried out only on flat surfaces. The printing systems and methods described herein, however, allow images to be printed on complex-shaped, i.e. non-planar, surfaces by depositing ink directly onto a transfer material 206 and then transferring the ink to a substrate. When printing directly onto a surface, print quality relies on accuracy of ink drop placement. Therefore, maintaining a constant or nearly constant distance between the printer head 202 and the flat surface of the transfer material 206 is necessary. Airflow, velocity variability, etc., can affect drop placement even when the change in distance is small, e.g. a few millimeters.
In some embodiments, a light source 204 cures some or all of the ink 208 deposited on the transfer material 206 by the printer head 202. The light source 204 may be configured to emit wavelengths of UV electromagnetic radiation of subtype V (UVV), subtype A (UVA), subtype B (UVB), subtype C (UVC), or any combination thereof. Generally, UVV wavelengths are those wavelengths measured between 395 nanometers (nm) and 445 nm, UVA wavelengths measure between 315 nm and 395 nm, UVB wavelengths measure between 280 nm and 315 nm, and UVC wavelengths measure between 100 nm and 280 nm. However, one skilled in the art will recognize these ranges are somewhat adjustable. For example, some embodiments may characterize wavelengths of 285 nm as UVC.
The light source 204 may be, for example, a fluorescent bulb, a light emitting diode (LED), a low pressure, e.g. mercury (Hg), bulb, or an excited dimer (excimer) lamp/laser. Combinations of different light sources could be used in some embodiments. Generally, the light source 204 is selected to ensure that the curing temperature does not exceed the temperature at which the ink 208 begins to sublime. For example, light source 204 of
Other curing processes may also be used, such as epoxy (resin) chemistries, flash curing, and electron beam technology. One skilled in the art will appreciate that many different curing processes could be adopted that utilize specific timeframes, intensities, rates, etc. The intensity may increase or decrease linearly or non-linearly, e.g. exponentially, logarithmically. In some embodiments, the intensity may be altered using a variable resistor or alternatively by applying a pulse-width-modulated (PWM) signal to the diodes in the case of an LED light source.
As shown in
Sublimation may require the transfer material 304, substrate 302, or both be heated up. As the sublimation process begins, some of the dye or pigment within the ink sublimes, or is converted into a gas, and permeates/diffuses into the substrate 302. The sublimed dye re-solidifies within the substrate 302, thereby forming the intended or final image 308. In various embodiments, flexible dye formulations are used that allow the image 306 to expand up to 500% of its original size during the sublimation process. Consequently, the final image 308 may not be the same size as the image 306 initially printed on the transfer material 304.
As shown in
When effective ink formulations are designed, a number of factors are considered, including flexibility, cross-linked density, ability to adhere to the substrate, and ink tack. Other factors can include the curing process utilized, substrate type, former type, the application(s) for which the substrate is to be used, etc. When printing onto complex-shaped substrates 404, it is important for the ink formulation(s) to be flexible. Flexibility allows the ink 406, i.e. image, to change shape without cracking, separating from the transfer material 402, or distorting at the same rate as the transfer material 402. Depending on the shape of the substrate 404, the image may need to stretch from 100% to 500% of its original size.
Various embodiments described herein are especially useful in combination with superflexible UV dye sublimation inks and thermoformable UV dye sublimation inks, such as are described in co-owned U.S. Pat. Nos. 7,427,317, 7,431,759, and 7,662,224, each of which is incorporated by reference herein. However, other ink formulations and technologies can also be used. Images printed using superflexible UV dye sublimation inks are known to extend up to 200% of their original size when heat is applied. Thermoformable UV dye sublimation inks, meanwhile, allow images to extend more than 400% of their original size when heat is applied.
Standard UV inks are typically formulated to have good adhesion and surface cure characteristics. This is done by modifying the cross-linked density and altering what monomers present that adhere to the transfer material 402 and/or substrate 404. However, the ink formulations used by the printing systems and methods described herein need not be designed to exhibit great adhesion or rub resistance. These inks are meant to have a relatively short lifetime before being transferred to the substrate 404.
The transfer material 402 can be removed from the surface of the substrate 404 once sublimation has completed, as shown in
At block 504, the printing system begins printing an image by depositing ink on the surface of a transfer material, e.g. thermoformable material, according to the printing instructions. The transfer material may be, for example, a thermoformable material such as an amorphous polymer. Formable transfer materials and substrates can include, for example, acrylonitrile butadiene styrene (ABS), polystyrene, polycarbonate, polyethylene, polypropylene, acrylics, e.g. casts and films, polyvinyl chloride (PVC), and vinyl copolymers. The instructions, meanwhile, can indicate where ink is to be deposited, what ink(s), transfer material(s), or substrate(s) are to be used, etc. In some embodiments, the printing system cures at least some of the ink deposited on the transfer material, as shown at block 506. For example, a UV LED light source can be used to cure thermoformable or superflexible UV dye sublimation ink. The UV LED light source can emit wavelengths within a certain range, e.g. UVC wavelengths. The range and/or UV subtype emitted by the light source may be selected to more effectively cure particular ink formulations used by the printing system. The ink is typically cured immediately or shortly after being deposited on the transfer material.
At block 508, the transfer material is formed to fit the complex-shaped surface of a substrate and, at block 510, the transfer material is pressed onto the complex-shaped surface. At block 512, the ink is heated to a temperature that is sufficient to cause some or all of the dye component within the ink to sublime and permeate the surface of the substrate. The transfer material, substrate, or both may be heated by the printing system or a distinct heating element. The required temperature may vary depending on the ink formulation, transfer material type, substrate type, etc. The temperature must be high enough to cause the ink to sublimate, but not so high as to damage the substrate or transfer material. At block 514, the transfer material is removed once sublimation has finished.
In some embodiments, residual ink is removed by jetting a solvent onto the surface of the transfer material, the substrate, or both, as shown at block 516. The residual ink is any ink that did not permeate the substrate, i.e. remains on the surface of the substrate or transfer material following sublimation. In such embodiments, the ink is soluble or solvent-sensitive, which allows excess ink to be easily removed by applying a solvent, such as water. Although the residual ink, which contains a depleted level of dye, is designed to dissolve during the washing process, the sublimed dye is not affected. Once transferred to the substrate, the sublimed dye is substantially insoluble with respect to the solvent used for washing.
At block 604, the rubber former, including the pre-distorted image, is prepared for sublimation and, at block 606, the rubber former is pressed onto the surface of the complex-shaped substrate. Typically, pressure is applied using a mold or some heat-resistant material, such as sand. At block 608, some combination of the substrate, rubber former, and mold/heat-resistant material are heated to a temperature sufficient to cause the ink to sublimate. Specific temperatures and/or periods of time may be used that improve the print quality of the resulting image.
At block 610, the rubber former is removed from the surface of the substrate. The mold and/or heat-resistant material is also removed if used to apply pressure or maintain the position of the rubber former. In some instances, residual ink will remain on the surfaces of the substrate and rubber former. If the ink formulation includes a soluble component, the residual ink can be removed by ejecting a solvent, e.g. water, onto the surfaces of the substrate and rubber former, as shown at block 612. If the ink formulations is sufficiently soluble, the rubber former can be reused for subsequent image transfers.
The bus 716 is illustrated as an abstraction that represents any one or more separate physical buses, point to point connections, or both connected by appropriate bridges, adapters, or controllers. The bus 716, therefore, can include, for example, a system bus, a Peripheral Component Interconnect (PCI) bus or PCI-Express bus, a HyperTransport or industry standard architecture (ISA) bus, a small computer system interface (SCSI) bus, a USB, IIC (I2C) bus, or an Institute of Electrical and Electronics Engineers (IEEE) standard 1394 bus, also called “Firewire.”
The computer system 700 may be a server computer, a client computer, a personal computer (PC), a user device, a tablet PC, a laptop computer, a personal digital assistant (PDA), a cellular telephone, an Android, an iPhone, an iPad, a Blackberry, a processor, a telephone, a web appliance, a network router, switch or bridge, a console, a hand-held console, a (hand-held) gaming device, a music player, any portable/mobile hand-held device, wearable device, or any machine capable of executing a set of instructions, sequential or otherwise, that specify actions to be taken by that machine.
The main memory 706, non-volatile memory 710, and storage medium 726 are computer-readable storage media that may store instructions 704, 708, 728 that implement at least portions of various embodiments. The instructions 704, 708, 728 can be implemented as software and/or firmware to program processor(s) 702 to carry out the actions described above.
The network adapter 712 enables the computer system 700 to mediate data in a network 714 with an entity that is external to the computer device 700, through any known and/or convenient communications protocol. The network adapter 712 can include a network adaptor card, wireless network interface card, router, access point, wireless router, switch, multilayer switch, protocol converter, gateway, bridge, bridge router, hub, digital media receiver, and/or repeater.
The techniques introduced here can be implemented by, for example, programmable circuitry, e.g. one or more processors, programmed with software and/or firmware, entirely in special-purpose hardwired, i.e. non-programmable, circuitry, or in a combination of such forms. Special-purpose circuitry may be in the form of, for example, one or more application-specific integrated circuits (ASICs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), etc.
The language used in the Detailed Description has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the technology be limited not by the Detailed Description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of various embodiments is intended to be illustrative, but not limiting, of the scope of the embodiments, which is set forth in the following claims.
This application is a division of U.S. patent application Ser. No. 14/732,447, filed on Jun. 5, 2015, now U.S. Pat. No. 9,844,963, which is a continuation-in-part of U.S. patent application Ser. No. 14/683,846, filed on Apr. 10, 2015, now U.S. Pat. No. 9,789,706, each of which is incorporated by reference herein.
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